21020001001 has 4 divisors (see below), whose sum is σ = 21933914112. Its totient is φ = 20106087892.

The previous prime is 21020000927. The next prime is 21020001071. The reversal of 21020001001 is 10010002012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21020001001 - 2¹¹ = 21019998953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21020001071) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 456956521 + ... + 456956566.

It is an arithmetic number, because the mean of its divisors is an integer number (5483478528).

Almost surely, 2^21020001001 is an apocalyptic number.

It is an amenable number.

21020001001 is a deficient number, since it is larger than the sum of its proper divisors (913913111).

21020001001 is an equidigital number, since it uses as much as digits as its factorization.

21020001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 913913110.

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21020001001 its reverse (10010002012), we get a palindrome (31030003013).

The spelling of 21020001001 in words is "twenty-one billion, twenty million, one thousand, one".